OIUKC'I'IOXS AM) DIKKHTLTIKS AND OTHKII THKOlII KS 225 



'protocone' always means the main anterointernal cusp <>f u normal 

 upper iiiitliirifonn tooth, whether that element is regarded as the original 

 primary cusp or otherwise. 



'The objection that the terms are not universally applicable is 

 scarcely worthy of consideration since they are widely applicable to the 

 p-eat majority of mammalian molar types, without in the least interfering 

 with the use of terms descriptive of 'relative position only,' which may 

 be used in any cases where Osborn's terms do not apply.'' 



Ailili ad ii in, December, 1000 (7 //v//n ///;. 



A careful study of the excellent series of Insectivore skulls in the National Museum, 

 while fully confirming Gidley's interpretation of the homologies of the molar cusps 

 (p. 124), yet does not sustain his broader conclusion that the paracone in normal 

 tritubercular molars is older than the protocone. 



(1) The upper molar pattern of I'utainoyale (Figs. 69, 69 ), is fundamentally similar 

 to that of Mt/ogale (Fig. 69 F). Its high central cusp is evidently composed of an 

 enlarged anterior and much reduced posterior cusp, and these cusps have the same 

 spatial and functional relations with the cusps of the lower teeth as the para- and 

 metacones of Myogale, while the low internal cusp functions like the protocone. 

 Sotf, /</*,,/ also has a low internal platform like that in JJyogale, but much reduced, 

 bearing two small cusps which function like the proto- and hypocones of Myogale. 

 The main high pointed cusp in Solenodon is surely equivalent to the large para- and 

 closely appressed reduced meta-cone of Potamogale. This high main cusp (pa + me) 

 is evidently less specialized in Potamogale than in Solenodon, Centetes, etc., and 

 further, the small basal, proto- and hypocones are in a more primitive condition in 

 Solenodon than in Centetes, where they are vestigial and now functionally replaced 

 by the enlarged high para- + metacone. In Hemicentetes the true protocone has 

 vanished and the teeth parallel the carnassials of Carnivora (p. 137), where the 

 protocone is likewise secondarily reduced. 



(2) Thus, contrary to the more usual view, the " trituberculy " of Centetes and 

 clii-ysochloris is a secondary acquirement or pseudotritubercufy, and the fact that 

 the high main cusp (pa + me) in Centetes develops in ontogeny more rapidly than the 

 vestigial internal ledge, or protocone, does not prove that in Potamogale, Myogale, 

 and in normal tritubercular molars the outer cusp (paracone) appeared phylogeneti- 

 cally earlier than the internal cusp (protocone). 



